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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development.

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/*
 * Copyright 2016 Author or Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.cp.elements.data.conversion.converters;

import static org.cp.elements.lang.ElementsExceptionsFactory.newConversionException;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.cp.elements.data.conversion.ConversionException;
import org.cp.elements.data.conversion.Converter;
import org.cp.elements.data.conversion.DefaultableConverter;
import org.cp.elements.lang.StringUtils;

/**
 * {@link DateConverter} converts an {@link Object } to a {@link Date}.
 *
 * @author John J. Blum
 * @see java.lang.Object
 * @see java.util.Date
 * @see org.cp.elements.data.conversion.DefaultableConverter
 * @since 1.0.0
 */
@SuppressWarnings("unused")
public class DateConverter extends DefaultableConverter {

  protected static final String DEFAULT_PATTERN = "MM/dd/yyyy hh:mm:ss a";

  private final DateFormat dateFormat;

  public DateConverter() {
    this(DEFAULT_PATTERN);
  }

  public DateConverter(String pattern) {
    this.dateFormat = new SimpleDateFormat(pattern);
  }

  protected DateFormat getDateFormat() {
    return this.dateFormat;
  }

  /**
   * Determines whether this {@link Converter} can convert {@link Object Objects}
   * {@link Class from type} {@link Class to type}.
   *
   * @param fromType {@link Class type} to convert from.
   * @param toType {@link Class type} to convert to.
   * @return a boolean indicating whether this {@link Converter} can convert {@link Object Objects}
   * {@link Class from type} {@link Class to type}.
   * @see org.cp.elements.data.conversion.ConversionService#canConvert(Class, Class)
   * @see #canConvert(Object, Class)
   */
  @Override
  public boolean canConvert(Class fromType, Class toType) {
    return isAssignableTo(fromType, Calendar.class, Date.class, Number.class, String.class)
      && Date.class.equals(toType);
  }

  /**
   * Converts an {@link Object} of {@link Class type S} into an {@link Object} of {@link Class type T}.
   *
   * @param value {@link Object} of {@link Class type S} to convert.
   * @return the converted {@link Object} of {@link Class type T}.
   * @throws ConversionException if the {@link Object} cannot be converted.
   * @see org.cp.elements.data.conversion.ConversionService#convert(Object, Class)
   * @see #convert(Object, Class)
   */
  @Override
  public Date convert(Object value) {

    if (value instanceof Calendar) {
      return ((Calendar) value).getTime();
    }
    else if (value instanceof Date) {
      return (Date) value;
    }
    else if (value instanceof Number) {
      return new Date(((Number) value).longValue());
    }
    else if (value instanceof String) {

      String valueString = String.valueOf(value).trim();

      try {
        return StringUtils.isDigits(valueString)
          ? new Date(Long.parseLong(valueString))
          : new Date(getDateFormat().parse(valueString).getTime());
      }
      catch (NumberFormatException | ParseException cause) {
        throw newConversionException(cause, "[%s] is not a valid date/time", value);
      }
    }
    else {
      return super.convert(value);
    }
  }
}